splais

My Feedback: (25)

I am building a really large (50%) size, non-aerobatic, plane that will have servo extensions of about exactly nine feet from the servo to the PowerBox coming from the elevator. I am wondering about this length, using two standard HD, 22ga, 48" extensions. So far, ground testing has shown no problem at all. Does anyone reading this have any actual experience with servo leads this long and would care to comment.

Also I have a 48" servo extension that is really HD with a red, blue and black wire. Does anyone know who's these are. thanks.

Thunderbolt47

My Feedback: (8)

Hey Splais, Once I took a bunch of extentions I had around the shop and had about 15 feet with about 14 or so connectors. I tested a servo and really didn't notice any problems either. Now I wouldn't recommend it. But it is a curious question.
Kelly

Tony Hallo

The table below lists the resistance of wire per foot for variuos gages. I would offer that the resistance of each connector plug is more than the 9 foot of 22 gage wire. If it were me, I would eliminate all plugs except for the one at the radio, solder the extension wire to the servo wire using one piece of wire. Every plug is another point of failure, why risk a 50% model?

Wire Gauge Resistance per foot
4 .000292
6 .000465
8 .000739
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
24 .0302
26 .0480
28 .0764

pe reivers

Time to make a quantum leap.
With such length you can easily loose one volt when using a digital servo at 5A current draw and 22 gauge wire.,A common plus and minus rail of 12 gauge would provide contant voltage to the servos for power, nearly load independant. Only the dedicated pulse signalline then runs from receiver to each servo.
The new Robbe/Futaba S-bus system also caters for this type of application.

Jezmo

One other item I try to use when running long extensions is using the twisted leads such as those sold by HiTec. It is supposed to help keep interference from getting into the signal wire. (Kinda like twisted pair network cable)

BarracudaHockey

My Feedback: (11)

I always get a chuckle out of that. (having installed network cabling and taught network troubleshooting at our local college)

mrbigg

My Feedback: (21)

I would go with 20 gauge wire with no connectors in between. When doing custom runs, I just get my wire from Radio shack. Red, Black, and Green. I put one end into the drill to twist them together. That way they stay bundled up. Put your connectors on the end. I've done quit a few big, expensive planes this way. They were scratchbuilt planes also, which to me, hold a higher value than a throw away ARF. In other words, I have no problem trusting this way of wiring up a big plane.

Tony Hallo

I did forget, I'd twist them too. Cost little extra and can't hurt.

BBW Walt

My Feedback: (11)

You can buy 20ga servo wire from Radical pre twisted, that's all you need. Crimp a plug on one the RX end and solder the servo to the other. You'll have no issue. http://www.radicalrc.com/category/Wi...and-Battery-64

sweetpea01

My Feedback: (10)

blue/red/black is Airtronics I believe.


I'd make a custom wire at that length.

pe reivers

Hey guys, any one ever calculated the voltage loss over 9 feet of wire with large (digital?) servo's? This is no small fry we are talking here, but a 50% plane. The word toy plane looses it's meaning in this kind of  twilight zone. 20 gauge wire will not cut it, believe me. This will be a small full size plane!

BarracudaHockey

My Feedback: (11)

Just out of curiosity, what do you guys think that twisting the wire does?

pe reivers

It changes the straight wires into a choke. Thus it can suppress very high frequency signals by facing these signals with a high resistance. The more winds (turns), the higher the resistance. Since resistance is used for the Ohm law, in this case we call it impedance., the power to block current flow. This is time depending. If the applied voltage is large enough, the current will in due time follow Ohm's law. In high frequencies, this will not happen, because the time is so very short.

Tony Hallo

I have found twisted pair wires on automotive crank and cam position sensors circuits, the twists per foot was stated right on the schematic. Also find them on the control systems at the plants were I work. So if GM, GE, Siemens throught it might help, who am I to argue?

It adds no more componets to fail and takes little time to twist so what's the dissavantage of using twisted wires?

When I stated flying giant scale, I used Ace noise traps on long leads, even resorted to a small capacitors across the signal to ground on a 12' Telemaster with Royal 1/4 scale servos. I then when to shielded wire from Bennett. Today the ignition systems are shielded much better so maybe you can get by. But I have experienced problems and take precautions were possible without inducing more points of failure.

Besides it looks better.

jkeze

My Feedback: (36)

Why dont you just put another receiver and battery pack pack there

Tony Hallo

I'm pretty sure that what's used in the Bill Hemphill 60% Cub, kind of distributive system rather than central. Good solution.
I really don't beleive the voltage drop is excessive, at 4 amps, the capacity of the plug, the voltage drop due to the length of 22 gage wire is .7 volt. With 20 gage as Walt suggested, we're looking at .4 volt, about the same as a 48" 22 gage extension that few would question. Using 6 volt batteries, the supply voltage to the servo is well above the lower rating of 4.8 volt. Of course we really don't know what servps are planned. Maybe they are Seiko's?

nonstoprc

My Feedback: (90)

Somebody has thought about a separate receiver/battery combo located at the tail section of "super" scale planes for elevators/rudder?

JoeAirPort

My Feedback: (41)

Yep several recivers/batteries in fact. Each wing half, tail, mid fuse.

ndb8fxe

My Feedback: (1)

Not an expert by far, so bear with me. Could the OP run a signal wire form the Rx and put just a battery out there near the servo thus not having the long run for servo power? Like I said I'm not an expert and this is just a thought.

pe reivers

yes he could. See post number 4. he can even have multiple batteries, as long as at least the minus line is connected to each other so a common voltage system is created, and no system can "float"

Magne

I think that the minus would also have to be connected to the receiver, but this could be just one common thin wire.

Magne

JoeAirPort

My Feedback: (41)

I don't think 0.4 volts using 20 gauge is that bad considering it's a worse case load of 4 amps. And no servo is going to pull that continuous. Maybe in a burst. We're talking about a fly it around cub here, not a TOC comp plane. With A123 at 6.6 volts you still will get 6.2 volts to each servo. You guys worry too much.

pe reivers

better safe than sorry. Large plane, dual servos on the aileron, add servo(s) for flaps, that makes three servos in each wing. Not the smallest ones either. Unless your plane total span is 9'. (That would reduce control forces by a factor of 4.)